HTTP Status Codes — Complete Reference
HTTP status codes are 3-digit numbers sent by servers to indicate the result of a request. Understanding them is essential for web development, API design, and SEO.
1xx — Informational
Continue
Server received request headers, client should continue.
Switching Protocols
Server agrees to upgrade the protocol (e.g., HTTP → WebSocket).
2xx — Success
OK
Request successful. Standard response for GET, POST, PUT.
Created
Resource successfully created. Used after POST.
No Content
Request succeeded but no content to return. Used after DELETE.
Partial Content
Partial content delivered (used for range requests / video streaming).
3xx — Redirection
Moved Permanently
Resource permanently moved. Browsers update bookmarks. SEO passes link equity.
Found
Temporary redirect. SEO does not pass link equity permanently.
Not Modified
Cached version is still valid. Browser uses its cached copy.
Temporary Redirect
Same as 302 but must keep the same HTTP method.
Permanent Redirect
Same as 301 but must keep the same HTTP method.
4xx — Client Error
Bad Request
Server can't understand the request. Usually a client-side syntax error.
Unauthorized
Authentication required. User must log in.
Forbidden
Authenticated but not authorized. Access denied.
Not Found
Resource not found. Most common web error.
Method Not Allowed
HTTP method not supported for this endpoint.
Conflict
Request conflicts with current state (e.g., duplicate entry).
Gone
Resource permanently deleted. Stronger signal than 404.
Unprocessable Entity
Request body is valid JSON but semantically incorrect.
Too Many Requests
Rate limit exceeded. Retry after delay.
5xx — Server Error
Internal Server Error
Generic server-side error. Check server logs.
Bad Gateway
Upstream server returned invalid response.
Service Unavailable
Server temporarily unavailable (maintenance or overload).
Gateway Timeout
Upstream server didn't respond in time.